This invention relates to an apparatus and method for mixing an epoxy resin and associated curing agent into an epoxy adhesive.
Epoxy materials are popular as adhesives due to their hardness, bonding strength, and their ability to harden with little or no shrinkage. Such adhesives typically include two constituents: an epoxy resin and a curing or hardening agent. The resin and curing agent are separately packaged until use, at which time they are combined to initiate curing.
Users of these adhesives do, however, encounter problems. Care must be taken when mixing the constituents by hand, because the constituents can be irritating to the skin and eyes, and they must be mixed in consistently accurate proportions. Users mixing and using epoxy adhesive in batches must cope with the change in the adhesive properties over curing time or "pot life". Further, cleaning of equipment used to mix and handle the epoxy adhesive is difficult, and solvents used for such cleaning can be hazardous. Prior art attempts to address some of these problems are shown, for example, in U.S. Pat. No. 4,090,262 to Schneider et al. granted May 16, 1978. Schneider shows separate tanks 1 and 2 for components "A" and "B" of a mixture, both being simultaneously propelled by a pressure source 3. Flow metering pumps 7 and 8 ensure that components A and B reach mixing chamber 16 in properly proportioned amounts. A hydraulic piston 14 positively cleans the mixing chamber. An alternate mixing chamber 20 has a stirring mechanism which must be cleaned with a solvent.
U.S. Pat. No. 2,894,732 to Taber et al. granted July 14, 1959, shows separate tanks 35 and 36 for a hardening agent and convertible resin. These components are propelled by pressure through fluid chambers 7 and 8, to a disposable mixing unit. A tube in the mixing unit is packed with metal chips 68 which cause the agent and resin to traverse "tortuous, irregularly intercommunicating flow passages", and thereby mix.
While these prior art arrangements function satisfactorily in meeting their specific requirements, they fail to adequately address the challenge of accurately and thoroughly mixing controlled amounts of epoxy adhesive and timing the dispensing of epoxy such that when used, it is consistently at or near a desired point in its curing stage.
It is therefore an object of the present invention to provide an apparatus to accurately and thoroughly mix the several components of an epoxy adhesive while requiring no direct operator contact. A further object is to reduce or eliminate the need to clean apparatus used to mix and dispense the adhesive. Yet another object of the invention is to enhance operator safety by minimizing direct contact in mixing and handling epoxy adhesive and its constituents.